//------------------------------------------------------------------------------
//  此代码版权（除特别声明或在XREF结尾的命名空间的代码）归作者本人若汝棋茗所有
//  源代码使用协议遵循本仓库的开源协议及附加协议，若本仓库没有设置，则按MIT开源协议授权
//  CSDN博客：https://blog.csdn.net/qq_40374647
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//  Gitee源代码仓库：https://gitee.com/RRQM_Home
//  Github源代码仓库：https://github.com/RRQM
//  API首页：https://touchsocket.net/
//  交流QQ群：234762506
//  感谢您的下载和使用
//------------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using TouchSocket.Resources;

namespace TouchSocket.Core
{
    /// <summary>
    /// 固定长度数据包处理适配器。
    /// </summary>
    public class FixedSizePackageAdapter : SingleStreamDataHandlingAdapter
    {
        /// <summary>
        /// 包剩余长度
        /// </summary>
        private int m_surPlusLength = 0;

        /// <summary>
        /// 临时包
        /// </summary>
        private ByteBlock m_tempByteBlock;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="fixedSize">数据包的长度</param>
        public FixedSizePackageAdapter(int fixedSize)
        {
            this.FixedSize = fixedSize;
        }

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        public override bool CanSendRequestInfo => false;

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        public override bool CanSplicingSend => true;

        /// <summary>
        /// 获取已设置的数据包的长度
        /// </summary>
        public int FixedSize { get; private set; }

        /// <summary>
        /// 预处理
        /// </summary>
        /// <param name="byteBlock"></param>
        protected override async Task PreviewReceivedAsync(ByteBlock byteBlock)
        {
            if (this.CacheTimeoutEnable && DateTime.UtcNow - this.LastCacheTime > this.CacheTimeout)
            {
                this.Reset();
            }
            var array = byteBlock.Memory.GetArray();
            var buffer = array.Array;
            var r = byteBlock.Length;
            if (this.m_tempByteBlock == null)
            {
                await this.SplitPackage(buffer, 0, r).ConfigureAwait(false);
            }
            else
            {
                if (this.m_surPlusLength == r)
                {
                    this.m_tempByteBlock.Write(new ReadOnlySpan<byte>(buffer, 0, this.m_surPlusLength));
                    await this.PreviewHandle(this.m_tempByteBlock).ConfigureAwait(false);
                    this.m_tempByteBlock = null;
                    this.m_surPlusLength = 0;
                }
                else if (this.m_surPlusLength < r)
                {
                    this.m_tempByteBlock.Write(new ReadOnlySpan<byte>(buffer, 0, this.m_surPlusLength));
                    await this.PreviewHandle(this.m_tempByteBlock).ConfigureAwait(false);
                    this.m_tempByteBlock = null;
                    await this.SplitPackage(buffer, this.m_surPlusLength, r).ConfigureAwait(false);
                }
                else
                {
                    this.m_tempByteBlock.Write(new ReadOnlySpan<byte>(buffer, 0, r));
                    this.m_surPlusLength -= r;
                    if (this.UpdateCacheTimeWhenRev)
                    {
                        this.LastCacheTime = DateTime.UtcNow;
                    }
                }
            }
        }



        /// <inheritdoc/>
        protected override async Task PreviewSendAsync(ReadOnlyMemory<byte> memory)
        {
            var dataLen = memory.Length;
            if (dataLen != this.FixedSize)
            {
                throw new OverlengthException(TouchSocketCoreResource.ValueMoreThan.Format(nameof(memory.Length), this.FixedSize));
            }
            var byteBlock = new ByteBlock(this.FixedSize);

            byteBlock.Write(memory.Span);

            byteBlock.SetLength(this.FixedSize);
            try
            {
                await this.GoSendAsync(byteBlock.Memory).ConfigureAwait(false);
            }
            finally
            {
                byteBlock.Dispose();
            }
        }

        /// <inheritdoc/>
        protected override async Task PreviewSendAsync(IList<ArraySegment<byte>> transferBytes)
        {
            var length = 0;
            foreach (var item in transferBytes)
            {
                length += item.Count;
            }

            if (length != this.FixedSize)
            {
                throw new OverlengthException(TouchSocketCoreResource.ValueMoreThan.Format(nameof(length), this.FixedSize));
            }
            var byteBlock = new ByteBlock(this.FixedSize);

            foreach (var item in transferBytes)
            {
                byteBlock.Write(new ReadOnlySpan<byte>(item.Array, item.Offset, item.Count));
            }

            byteBlock.SetLength(this.FixedSize);
            try
            {
                await this.GoSendAsync(byteBlock.Memory).ConfigureAwait(false);
            }
            finally
            {
                byteBlock.Dispose();
            }
        }

        /// <summary>
        /// <inheritdoc/>
        /// </summary>
        protected override void Reset()
        {
            this.m_tempByteBlock.SafeDispose();
            this.m_tempByteBlock = null;
            this.m_surPlusLength = 0;
            base.Reset();
        }

        private async Task PreviewHandle(ByteBlock byteBlock)
        {
            try
            {
                byteBlock.Position = 0;
                await this.GoReceivedAsync(byteBlock, null).ConfigureAwait(false);
            }
            finally
            {
                byteBlock.Dispose();
            }
        }

        private async Task SplitPackage(byte[] dataBuffer, int index, int r)
        {
            while (index < r)
            {
                if (r - index >= this.FixedSize)
                {
                    var byteBlock = new ByteBlock(this.FixedSize);
                    byteBlock.Write(new ReadOnlySpan<byte>(dataBuffer, index, this.FixedSize));
                    await this.PreviewHandle(byteBlock).ConfigureAwait(false);
                    this.m_surPlusLength = 0;
                }
                else//半包
                {
                    this.m_tempByteBlock = new ByteBlock(this.FixedSize);
                    this.m_surPlusLength = this.FixedSize - (r - index);
                    this.m_tempByteBlock.Write(new ReadOnlySpan<byte>(dataBuffer, index, r - index));
                    if (this.UpdateCacheTimeWhenRev)
                    {
                        this.LastCacheTime = DateTime.UtcNow;
                    }
                }
                index += this.FixedSize;
            }
        }
    }
}